EncryptTargetColumnOfCSV.java

	public static void main(String[] args) throws Exception {
		String inFilePath = args[0];
		int targetColumn = Integer.parseInt((args[1]));
		String outFilePath = args[2];

		File inCsv = new File(inFilePath);
		File outCsv = new File(outFilePath);

		BufferedReader br = null;
		FileInputStream fis = null;
		PrintWriter pw = null;
		FileOutputStream fos = null;
		try {
			fis = new FileInputStream(inCsv);
			br = new BufferedReader(new InputStreamReader(fis, "UTF-8"));
			fos = new FileOutputStream(outCsv);
			pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(fos, "UTF-8")));
			String line = null;
			while (br.ready()) {
				line = br.readLine();
				StringBuilder sb = new StringBuilder();

				StringTokenizer st = new StringTokenizer(line, ",");
				for (int i = 1; st.hasMoreTokens(); i++) {
					if (i > 1) {
						sb.append(",");
					}
					if (i == targetColumn) {
						sb.append(encrypt(st.nextToken()));
					} else {
						sb.append(st.nextToken());
					}
				}
				pw.println(sb.toString());
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (pw != null) {
					pw.close();
				}
				if (fos != null) {
					fos.close();
				}
				if (br != null) {
					br.close();
				}
				if (fis != null) {
					fis.close();
				}
			} catch (Exception ignore) {

			}
		}
	}

	private static String encrypt(String val) throws Exception {
		val = val.substring(1, val.length() -1);
		val = printDigest(getStringDigest(val));

		return "\"" + val + "\"" ;
	}

	private static byte[] getStringDigest(String data) throws Exception {
		MessageDigest md = MessageDigest.getInstance("SHA-256");
		byte[] dat = data.getBytes();
		md.update(dat);
		return md.digest();
	}

	private static String printDigest(byte[] digest) {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < digest.length; i++) {
			int d = digest[i];
			if (d < 0) {
				d += 256;
			}
			if (d < 16) {
				sb.append("0");
			}
			sb.append(Integer.toString(d, 16));
		}
		return sb.toString();
	}